Airfoil construction



n 30 1964 E. H. SCHNEIDER 3,139,247

AIRFOIL CONSTRUCTION Filed Feb. 7, 1963 United States. Patent D 3,139,247 AHQFOIL CONSTRUCTION Edwin H. Schneider, 250 Meigs St., Rochester 7, N.Y. Filed Feb. 7, 1963, Ser. No. 256,935 6 Claims. (Cl. 244-41) This invention relates to the construction of an airfoil, particularly intended for use as a wing of an aircraft, and it will be described in connection with a wing as a convenient example, but the airfoil design of the present invention is useful also for other control surfaces, such as the elevator, rudder, or stabilizer.

An object of the invention is the provision of a generally improved and more satisfactory airfoil construction.

Another object is the provision of an airfoil which provides greater lift in proportion to drag than has been possible with comparable airfoils of the prior art.

These and other desirable objects may be attained in the manner disclosed as an illustrative embodiment of the invention in the following description and in the accompanying drawings forming a part hereof, in which:

FIG. 1 is a schematic cross section through an airfoil such as a wing, illustrating the invention; and

FIG. 2 is a fragmentary plan of the airfoil surface modified according to the present invention.

Shown somewhat schematically in the drawings is a typical airfoil such as a wing, having longitudinal stiffening members such as the spars 11 and 13, extending the length of the wing, the spars supporting the usual ribs (not shown) which extend transversely of the wing, the spars and ribs together serving to support the skin or envelope surfaces, usually of light metal sheeting (for example, aluminum sheets) shown at 15 on the under side of the wing and at 17 on the top surface of the wing. Except for the special features of the invention as further described below, the exact shape of the airfoil surfaces may be conventional. For convenience of illustration, the bottom surface 15 is shown as straight, but it may be suitably curved in known manner. The upper surface 17 is normally curved convexly from the blunt rounded forward edge or nose 19 up to a high point 21 part way back from the nose, and top surface 17 then continues rearwardly in the conventional smooth manner (except for the special features of the present invention as described below) either flat or concave or convex or any conventional shape known in the art, to the rear edge or trailing edge 23.

The feature of the present invention is that this top surface 17 is provided, at a point preferably a little to the rear of the high point 21, with a series or multiplicity of conical depressions 25 arranged side by side in one or more rows, each row extending in a general direction along the length of the wing throughout all or any desired portion of such length. Each conical or approximately conical depression 25 has a base diameter considerably bigger than its depth at the deepest point or apex. The proportions may be varied considerably. Merely as an example, each of these conical depressions may have a base circle of about four inches to eight inches in diameter, and a depth at the apex of one to two inches. They may more appropriately be called cone-like rather than conical, because they need not be strictly conical in a geometrical sense, it being possible to make them pyramidal, having polygonal bases, or having bases of elliptical or other curved but non-circular shape. In general, however, they all approximate the shape of an inverted cone, and all constitute depressions in the otherwise smooth top surface 17 of the airfoil.

According to the invention, approximately the rear half of the area of the cone-like depression is completely 3,139,247 Patented June '30, 1 964 able or significant with respect to the area of the airfoil.

It is well understood in the art that the lift of an airfoil section used as a wing, for example, is not caused by super-atmospheric pressure on the bottom surface, but rather by sub-atmospheric pressure or partial vacuum created at the top surface. The cone-like depressions of the present invention are found in practice to create an appreciably greater vacuum orsub-atmospheric pressure over the area of the depression, thereby increasing the lift to an extent more than sufficient to make up for the additional drag caused by the slightly greater weight per unit of area of airfoil surface containing these depressions, than of similar airfoil surface of conventional smooth kind without the depressions. The exact aerodynamic theory as to why the depressions 25 in combination with the partial covers 27 should increase the vacuum, is not fully understood at present. It is sufficient to say that the increased vacuum, and hence increased lift, actually does occur, regardless of the lack of understanding as to the exact scientific reasons or aerodynamic principles which cause it.

While an airplane is standing on the ground, rain water may accumulate in the depressions of the present invention. However, when flight starts, the rapid rush of air over the airfoil surface will quickly scour out any water in the depressions, leaving them as dry as the rest of the surface of the airfoil. if the airfoil is used in climates or at altitudes where snow or sleet are likely to be encountered, a duct 31 for hot exhaust gases from the engine may be built into the wing, running along the length of the wing directly under the various depressions 25, to heat the cone-like surfaces of the depressions so as to melt snow or ice.

It is seen from the foregoing disclosure that the objects and purposes of the invention are well fulfilled. It is to be understood that the foregoing disclosure is given by way of illustrative example only, rather than by way of limitation, and that without departing from the invention, the details may be varied within the scope of the appended claims.

What is claimed is:

I. An airfoil structure having a generally smooth surface extending from a leading edge to a trailing edge, the general smoothness of said surface being interrupted by a series of cone-like depressions of substantially greater diameter than depth, and means forming a stationary cover over the forward portion of each cone-like depression, the rear portion thereof being uncovered and open.

2. An airfoil structure comprising means forming an exposed skin member over which air passes in flight, said skin member being approximately smooth in general and having a multiplicity of shallow cone-like depressions therein, a portion of said skin member continuing unbroken to form a cover over the forward portion only of each cone-like depression, the rear portion of each cone- 5. An airfoilmember comprising a metal sheet having an outer face over which air passes in flight and an inner face not exposed to substantial passage of air in flight, said metal sheet having a series of approximately semi-circular openings therein, and a series of sheet metal cone members each having a diameter several times as great as its height, each cone member being fixed to the inner face of said metal sheet in surrounding relation to one of said semi-circular openings in such position that the apex of the cone member is substantially directly beneath the mid point of the straight side of the semi-circular openmg.

6. An aircraft airfoil having one exterior surface subjected to partial vacuum during normal flight, said surface having therein a series of conical depressions arranged in side by side relation to each other along a line transverse to the direction of flight, the surface of the airfoil being substantially smooth immediately around and between the depressions, each depression having smooth walls of conical shape meeting at a sharply pointed apex, the depth of the depression from its base circle to its apex being substantially less than the diameter of its base circle, and a permanent fixed Wall forming a cover over only substantiallythe forward half of the base circle a of each depression, substantially the rear half of the base circle of each depression being uncovered and completely open, said permanent fixed wall forming a smooth con tinuation of the smooth surface of the airfoil around and between the depressions, said series of conical depressions with fixed covers over-their forward halves tending to increase the vacuum on said exterior surface of said airfoil, thereby tending to increase the lift thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,084,068 Burleigh Jan. 13, 1914 1,152,426 McCarroll Sept. 7, 1915 1,361,277 Mott Dec. 7, 1920 1,848,555 Wilford Mar. 8, 1932 2,261,558 OrloiT NOV. 4, 1941 2,556,736 Palmatier June 12, 1951 2,783,008 Bodine Feb. 26, 1957 2,899,150 Ellis Feb. 12, 1959 V FOREIGN PATENTS 206,880 Great Britain Nov. 22, 1923 730,121 Great Britain May 18, 1955 

1. AN AIRFOIL STRUCTURE HAVING A GENERALLY SMOOTH SURFACE EXTENDING FROM A LEADING EDGE TO A TRAILING EDGE, THE GENERAL SMOOTHNESS OF SAID SURFACE BEING INTERRUPTED BY A SERIES OF CONE-LIKE DEPRESSIONS OF SUBSTANTIALLY GREATER DIAMETER THAN DEPTH, AND MEANS FORMING A STATIONARY COVER OVER THE FORWARD PORTION OF EACH CONE-LIKE DEPRESSION, THE REAR PORTION THEREOF BEING UNCOVERED AND OPEN. 